Bug#963962: /etc/grub.d/20_linux_xen generates non-functional menu entries

[Sergio Gelato]

Package: grub-common
Version: 2.02+dfsg1-20
Severity: normal

xen-hypervisor-4.11-amd64 in buster installs the following files:

/boot/xen-4.11-amd64.gz
/boot/xen-4.11-amd64.efi
/boot/xen-4.11-amd64.config

The first one is bootable (usually; but see #924360). The second one may or
may not be bootable by GRUB (I didn't succeed); it's probably meant for
booting directly by UEFI. The third is just a summary of the hypervisor's
build configuration and clearly not meant for booting.

/etc/grub.d/20_linux_xen generates boot menu entries for all three. This
seems excessive. The .config entry definitely shouldn't be there, and the
.efi one does not work in its present form (although for all I know this
may be fixable with better module settings).

At the very least the .config file should be filtered out by
file_is_not_sym(), grub_file_is_not_garbage() or similar.

The .efi file clearly also requires attention but I'm not going to suggest
a specific resolution yet. If GRUB can be made to boot it, maybe that would
help solve #924360 on affected hardware; otherwise it would be better not
to generate a menu entry for it (perhaps by not installing it in /boot,
which would be a matter for the Debian Xen maintainers).